Rishi Sunak’s campaign to be Britain’s next prime minister was endorsed on Tuesday by Deputy Prime Minister Dominic Raab and transport minister Grant Shapps, who ditched his own leadership bid to back him.

“I know that Rishi has got what it takes. He’s got what it takes to provide the leadership that we need to steer the country through tough economic times,” Raab said, introducing Sunak at his campaign launch event.

Shapps announced on Twitter he was abandoning his bid, saying Sunak had the “competence and experience” to lead the country.

Meanwhile, Sunak has kicked off his campaign today promising “honesty”, in a increasingly testy and divisive battle to succeed Boris Johnson.

An initial 11 candidates put their names forward to become leader of the governing Conservative Party and Britain’s next premier after Johnson was forced to say he would step down when support drained from him over a series of scandals.

Only those who get nominations from 20 of their 358 Conservative colleagues in parliament on Tuesday will go forward to the first vote on Wednesday. The field will be then be quickly whittled down a final two, with Conservative Party members making the final decision.

Britain’s economy is facing rocketing inflation, high debt, and low growth, with people coping with the tightest squeeze on their finances in decades, all set against a backdrop of an energy crunch exacerbated by the war in Ukraine which has sent fuel prices soaring.

As the contest heated up, rival campaigns stepped up private criticism of each other and pointed to either financial or other questions hanging over their opponents.

With most candidates saying they would cut taxes if they win, Sunak, the current bookmakers’ favourite, has sought to portray himself as the serious candidate, promising “grown up” honesty “not fairy tales”.

“It is not credible to promise lots more spending and lower taxes,” said Sunak,

As finance minister, Sunak set Britain on course to have its biggest tax burden since the 1950s, and the other prime ministerial hopefuls have turned their fire on him on tax, with most saying they would oversee cuts immediately.